From Asking Hashem by Rabbi Avigdor Miller
The Chovos Halevavos says that the beginning of serving Hashem is to be grateful to Him. However, in order to be grateful, we must appreciate what’s being done for us. We can’t be grateful if we don’t think it’s something good for us; we’ll always think Hashem is still missing, more should have been done for us.
Suppose a man has a colostomy. When he wants to move his bowels he has to unscrew the lid of a special contraption attached to his side. The good old days are gone forever. If he had any sense he would have thanked Hashem when he was normal.
We have to understand what Hashem is doing for us
When we look at a man like that, we shouldn’t let the opportunity go lost; we have to say “rofai chol basar” (Asher Yatzar). A visit to the bathroom is a time for Hallel. We should be very happy, full of joy. Here is an example of another man who forgot what it means to urinate: For years and years, three times a week, he’s linked up to a kidney machine. The wealthy man has a kidney machine in his own house. Three times a week he has to spend a couple of hours on it. He cannot cleanse his body of the wastes otherwise. Without a machine he’s a dead man.
However, we’re carrying around a miniature kidney machine — not only one, we have two, one for a spare. If that man could get just one, he’d be delirious with happiness. He looks with great envy at people as they walk down the street. We have to spend our lives understanding what Hashem is doing for us.